In general, amplifiers are used to increase the power of signals. For example, amplifiers can be used to convert low-power radio frequency (RF) signals into higher power RF signals for driving the antenna of a transmitter. In such cases, amplifiers may be implemented as part of an overall power amplifier used by an RF transmission system.
One common issue with amplifiers is bandwidth. For example, many amplifier designs with high theoretical power efficiencies may have characteristically lower fractional bandwidths, where the fractional bandwidth is the bandwidth of the amplifier divided by the center frequency of the amplifier. This can make it difficult to provide an amplifier with both high efficiency and high bandwidth.
A variety of factors can limit bandwidth in amplifiers. For example, parasitic and other capacitances can reduce the functional bandwidth of an amplifier. There remains a need for amplifiers that can provide relatively high bandwidths and low frequency gains.